Improvements in and relating to pile foundations

ABSTRACT

A pile ( 270 ) within a bore ( 110 ) comprises a column ( 250 ). The column ( 250 ) comprises a stack of a plurality of pile sections ( 300 ) arranged end-to-end within the bore ( 110 ). There is a cured material ( 260 ) between at least a part of an outside surface of the column ( 250 ) and the surface of the bore ( 110 ). The cured material, for example grout, may be provided through channels in the pile sections.

FIELD OF THE INVENTION

The present invention concerns piles. More particularly, but not exclusively, this invention concerns a pile within a bore and a method and a kit of parts for forming the same. The invention also concerns a building including a pile within a bore and a method of forming the same.

BACKGROUND OF THE INVENTION

Piles are deep foundations providing support for buildings or other structures. They are typically long, narrow columns of reinforced concrete or steel. Prior-art piles include pre-cast concrete piles that are driven into the ground using a pile-driver and cast solid concrete piles that are formed by digging a bore in the ground (typically using an auger), pouring concrete directly into the hole and allowing it to set.

WO 2008/047151 A1 (City University) discloses a method of forming a pile comprising: forming a bore in the ground to a required depth; disposing a cylinder in the bore; filling the bore with uncast concrete so that, on hardening, a cast concrete pile is formed in the bore, the pile having a longitudinal cavity permitting access to the pile along at least a portion of its length. The longitudinal cavity is sufficiently wide to allow access to the longitudinal cavity so that cast concrete can be tested at a time after construction.

The approach in WO 2008/047151 can be relatively time-consuming. There also is a risk that voids or other faults will form in the pile when it is cast underground, as the bore in which it is cast can have unpredictable or unhelpful wall properties. Voids or other faults can result in weaknesses in the cast concrete pile. Although the longitudinal cavity provides some access for testing the cast concrete, there remains a risk that faults go undetected.

The present invention seeks to mitigate the above-mentioned problems.

SUMMARY OF THE INVENTION

A first aspect of the invention provides a method of forming a pile within a bore, the method comprising:

stacking a plurality of hollow pile sections end-to-end within the bore to form a column, there being a gap between at least a part of an outside surface of the column and the surface of the bore;

filling the gap with a curable liquid material ; and curing the liquid material.

A second aspect of the invention provides a method of constructing a building, the method including forming a pile within a bore by the method of the first aspect of the invention.

A third aspect of the invention provides a pile within a bore, the pile within a bore having the features set out in claim 8 below.

A fourth aspect of the invention provides a building including a pile within a bore according to the third aspect of the invention.

A fifth aspect of the invention provides a kit of parts having the features set out in claim 15 below.

It will of course be appreciated that features described in relation to one aspect of the present disclosure may be incorporated into other aspects of the present disclosure. For example, the method of the present disclosure may incorporate any of the features described with reference to the apparatus of the present disclosure and vice versa.

DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described by way of example only with reference to the accompanying schematic drawings of which:

FIGS. 1a to 1h are a sequence of side views of a pile being formed, according to a first embodiment of the present disclosure;

FIG. 2 is a perspective view of a pile section according to a second embodiment of the present disclosure;

FIG. 3 is a perspective view of a pile section according to a third embodiment of the present disclosure;

FIG. 4 is a perspective view of a pile section according to a fourth embodiment of the present disclosure;

FIG. 5 is a side view of a pair of pile sections according to a fifth embodiment of the present disclosure;

FIG. 6 is a plan view of a pile section according to a sixth embodiment of the present disclosure; and

FIG. 7 is a plan view of a pile section according to a seventh embodiment of the present disclosure;

DETAILED DESCRIPTION

A first aspect of the invention provides a method of forming a pile within a bore, the method comprising:

-   -   stacking a plurality of hollow pile sections end-to-end within         the bore to form     -   a column,         -   there being a gap between at least a part of an outside             surface of the column and the surface of the bore;     -   filling the gap with a curable liquid material; and     -   curing the liquid material.     -   The pile sections may be tubular pile sections; thus, the column         may be a tube.

The pile sections are preferably concrete. The pile sections are preferably pre-formed (for example pre-cast) at a location remote from the location at which the pile is to be formed. The method may comprise the step of receiving the pile sections from a remote location.

The surface of the bore will be understood to be the surface of the surrounding soil into which the bore is made (typically longitudinally and circumferentially extending).

The method may include the step of joining together a plurality of section components to form each pile section. The section components are preferably pre-formed (for example pre-cast) at a location remote from the location at which the pile is to be formed. The method may comprise the step of receiving the plurality of section components from a remote location, and then joining together the plurality of section components to form each pile section.

The curable liquid, when in place and cured, is preferably configured to transfer the skin friction generated at the interface with the pile bore to the interface between the grout and the sections of the pile.

The curable liquid material may be grout. The grout may comprise reinforcing material. Alternatively, the curable liquid material may be for example resin.

Advantageously, grout is not concrete. Providing a pile formed from a stack of pile sections and then filling the gap between the pile and the bore, with the curable liquid, has been found to be especially advantageous because it tends to be possible to use on a variety of soil types (whereas the pile in WO 2008/047151 tends to be limited to use of clay soils).

The method may include the step of pouring the curable liquid material directly into the gap. The curable liquid material may be inserted under relatively low pressure.

The method may comprise the step of applying additional curable liquid material after the previous liquid material has cured. The additional curable liquid material may be supplied at relatively high pressure, for example such that it cracks and percolates through the first cured material. This step may be advantageous on fine soils as it enables the additional curable liquid to percolate into the soil. The additional curable liquid material may be grout, preferably finer grout than the first curable liquid material.

The method may include the step of directing the curable liquid material into the gap through channels in the sections. The stacking may include aligning the channels of one section with the channels of an adjacent section, such that the liquid material may flow from the channel in one section to the channel in an adjacent section. Alignment may be achieved visually but is more preferably achieved via an alignment arrangement (such as interlocking male and female members located at a common location on the opposing ends of the adjacent pile sections). The adjacent pile sections may be configured to be self-aligning (for example they may comprise suitable inclined surfaces to ensure correct alignment as the adjacent sections are stacked together).

The method may include the step of digging the bore, for example using an auger.

The method may include the step of forming impressions into the interior wall of the bore.

The method may include lowering the pile sections into the bore sequentially, for example one-at-a-time.

The column may have a length that is substantially the same as the depth of the bore. The column may be shorter than the depth of the bore. The column may for example have a length that is between half the depth of the bore, and the full depth of the bore. Alternatively, the column may be longer than the depth of the bore.

The column may have a length that is more than three times its breadth. The gap may be continuous. The gap may extend across the majority, (preferably, all or substantially all) of the outside surface of the column and the surface of the bore. The gap may be substantially uniform around the outside surface of the column.

The curable liquid material may fill all or substantially all of the gap. The method may comprise the step of installing a pile cap on the top of the final pile section to close off the top of the stack of pile sections. The method may comprise the step of selecting the pile cap from a plurality of differently-sized (more preferably different length) pile caps. The pile caps may be pre-cast. This may ensure the correct height of the pile may be obtained (for example a relatively short cap can be provided if the stack of pile sections is relatively tall in the bore, and likewise a relatively long cap can be provided if the stack of pile sections is relatively short in the bore).

Before placing the stack of pile sections into the bore, the method may comprise the step of initially installing a pile base piece in the base of the bore, to close off the base of the pile. The pile base piece may facilitate increased end bearing resistance of the pile. The pile base piece may be shaped to facilitate increased end bearing resistance of the pile.

A second aspect of the invention provides a method of constructing a building, the method including forming a pile within a bore by the above-mentioned method. A third aspect of the invention provides a pile within a bore, comprising:

a column comprising a stack of a plurality of pile sections arranged end-to-end within the bore, and a cured material between at least a part of an outside surface of the column and the surface of the bore.

The plurality of pile sections may include pile sections that have different widths from each other. The column may taper in width, for example so that it has a smaller width at its base and a larger width at its top (or vice versa). Thus, the pile sections forming the column may increase in width with height up the column (or vice versa). The pile sections may have the same internal width (e.g. internal diameter). A taper in the column may be achieved by varying the thickness of the wall of adjacent pile sections. In embodiments comprising a channel configured to allow the transport of a curable liquid material along the length of the column, a channel in each pile section may be at the same spacing (e.g. radius) from the centre of the column. That spacing may be defined by the smallest width pile section.

The pile sections may be tubes. The tubes may have a constant inner width along the height of the column (even in embodiments in which the outer width of the tubes is not the same along the height of the column, for example where the tubes forming the column increase in width with height up the column). The tubes may have an internal width that is at least half their external width.

The pile sections may be circular in cross-section. The pile sections may be polygonal in cross-section.

The pile sections may comprise elements (for example castellations) at each of their axial ends, the axial end elements being sized and shaped to interlock with the corresponding axial end elements of another of the pile sections.

The pile sections may comprise a plurality of section components. Each pile section may for example be made from between 2 and 10 section components. The plurality of section components may be identical to each other. The section components may be segments of an annulus. Providing section components in each pile section may facilitate efficient transport of the components of the pile (compared to transporting fully assembled, or cast, pile sections).

Each pile section, and preferably each pile section component, may comprise elements (for example, tongue-and-groove elements) at each axial end, sized and shaped to interlock with the corresponding elements of another of the pile section/pile section component. The method may comprise the step of joining adjacent pile sections together, for example with a fastener.

At least some of the pile sections may include a raised and/or indented pattern on their outer surfaces, i.e. a textured pattern. The pattern may be irregular.

Alternatively, the pattern may be a regular pattern of repeating shapes. Such an arrangement may facilitate effective binding of the curable liquid to the outer surface of the sections and/or increase the resistance between the outer surface of the pile and the cured liquid. At least some of the sections may include protrusions on their outer surface, which may be arranged in a regular pattern. The protrusions may be dome-shaped.

At least some of the sections may include channels configured to allow the transport of a curable liquid material along the length of the column. The channels may be within the sections, for example entirely enclosed in the solid material of the sections (save at inlets and outlets). The channels may be wholly or partly on the surface of the sections, for example the channels may be exposed channels running along a face of the sections. The channels may comprise transport channels in fluid communication with outlet channels. The transport channels may be vertical. The outlet channels may be horizontal. The transport channels may be in fluid communication with the outlet channels. There may, for example, be a multiplicity, for example 1 to 10, transport channels in each pile section. The transport channels may be at the same radial position in each pile section in the column.

The hollow pile sections may be concrete, for example pre-cast concrete. Use of pre-cast concrete has the advantage that the pile sections (or the section components) can be manufactured remotely from the site of the bore and then transported to the bore for use. Manufacturing the pile sections (or the section components) as pre-cast concrete, before their use in the bore, has the advantage that quality checks can be carried out on them before their installation in the ground. The pile sections may be reinforced concrete.

A fourth aspect of the invention provides a building including a pile within a bore, as described herein. The pile may be load-bearing within the building.

A fifth aspect of the invention provides a kit of parts for forming a pile within a bore, the kit comprising:

a plurality of pile sections, wherein

-   -   the plurality of pile sections are configured to be stacked         end-to-end to form a column,     -   the number of pile sections corresponds to a length of the         column, said     -   length being equal to at least half of the depth of the bore;         and

a curable liquid material.

The invention will now be more fully understood and further advantages will become apparent when reference is made to the following detailed description of embodiments of the invention, wherein like reference numerals denote similar elements.

FIG. 1a to 1h show in side view an example embodiment of the method of forming a pile. In FIG. 1a , bore 110 has been excavated in the ground 10 using an auger (not shown), which has been operated by piling rig 100. Piling rig 100 includes attachment point 102 that is used to attach various apparatus that is to be lowered into bore 110. (For example, the auger was attached to attachment point 102 during the digging of the bore 110).

In FIG. 1b , impression-forming attachment 104 is attached to attachment point 102 and is lowered into bore 110. Impression-forming attachment 104 comprises a plurality of impression-forming elements 106 that are configured to form impressions in the interior wall of bore 110 when impression-forming attachment 104 is actuated to expand outwards in a radial direction. The actuation and expansion of impression forming attachment 104 is shown in FIG. 1c . Impression forming elements 106 are pressed into the wall of bore 110 to form impressions 112. Impression forming attachment 104 is then withdrawn from bore 110 by piling rig 100 as shown in FIG. 1d . The result of this operation as shown in FIGS. 1b to 1d is that impressions 112 are formed in the wall of bore 110.

An advantageous effect of impressions 112 is that when the pile is finally constructed, the skin friction between the pile and the bore is increased, thereby increasing the pull-out resistance and/or providing a piling structure that better reacts loads into the ground. However, this feature is not essential to the invention and in alternative embodiments of the present disclosure, the steps of FIGS. 1b to 1d may be omitted, and substantially no impressions are formed in the wall of bore 110.

In FIG. 1e , pile section 200 a has been attached to attachment point 102. Pile section 200 a is a hollow cylinder of prefabricated concrete. Piling rig 100 lowers pile section 200 a into bore 110 as indicated by directional arrow 105.

Successive pile sections 200 b, 200 c, 200 d, 200 e are attached to attachment point 102 and lowered into bore 110 respectively in turn. As shown in FIG. 1f , each successive pile section is stacked on top of the previous section to form vertical column 250. Dashed line 202 indicated the continuous inner surface of hollow column 250. The size of pile sections 200 a-200 e is selected such that when pile sections 200 a-200 e are stacked to form column 250, there is a gap 114 between the outer surface of column 250 and the inner surface of bore 110. While column 250 has a length that is substantially the same as the height of bore 110, in alternative embodiments of the present disclosure column 250 may have a length that is shorter than the height of the bore, for example, to leave some space at the top of bore 110 for other structural features in the construction. Indeed, the length of column 250 may correspond to between half the height of bore 110, and the full height of bore 110. In alternative embodiments of the present disclosure, the length of column 250 may correspond to a height greater than the height of bore 110.

FIG. 1g shows that grout 260 is poured into gap 114. The insertion of grout 260 is indicated by directional arrow 113.

FIG. 1h shows that grout 260 has filled gap 114, including impressions 112 within the wall of bore 110. This forms completed pile 270. In alternative embodiments of the present disclosure, grout 260 may be an alternative curable liquid material, for example a resin. An advantage of grout is that it is light and cheap, and has relatively low viscosity (compared to more coarse materials such as concrete).

Column 250 is formed of concrete and can bear the majority of the primary longitudinal loads from any construction above. The grout is arranged to transfer the skin friction generated at the interface with the pile bore to the interface between the grout and the pre-cast sections of the pile (i.e. such that the loads can be reacted/transferred from the pile to the surrounding soil).

In alternative embodiments of the present disclosure, pile sections 200 a-200 e may comprise channels. Grout 260 is poured into the channels within column 250 to achieve a uniform distribution of grout 260 across the entire length of column 250. For example, FIG. 2 shows a perspective view of pile section 300 according to an embodiment of the present disclosure. Pile section 300 comprises vertical channels 302 in fluid communication with horizontal channels 304 (shown in dashed lines in FIG. 2). Vertical channels 302 are designed to allow for a vertical flow of curable liquid material through section 300. Horizontal channels 304 allow for the curable liquid material to flow out of pile section 300. In embodiments of the present disclosure, the curable liquid material would flow out of horizontal channels 304 and into a gap (such as gap 114 in the embodiments of FIGS. 1a-1e ).

In alternative embodiments of the present disclosure, vertical channel 302 is not entirely enclosed in the solid material of pile section 300. Instead vertical channel 302 may be an exposed channel running along the outside face of pile section 300.

FIG. 3 shows a perspective view of pile section 400 according to an embodiment of the present disclosure. Pile section 400 comprises textured pattern 402 on its exterior surface. Textured pattern 402 comprises protrusions that extend outwardly from the surface of pile section 400. These protrusions have the effects of increasing the friction between the outer surface of pile section 400 and any grout that may be in contact with it (such as grout 260 in the embodiments of FIGS. 1a-1h ). In embodiments of the present disclosure, textured pattern 402 may be irregular. In embodiments of the present disclosure, textured pattern 402 may be a regular pattern of repeating shapes.

FIG. 4 shows a perspective view of pile section 500 according to an embodiment of the present disclosure. Pile section 500 comprises regular, circular-shaped protrusions 502 at regular intervals around the outer surface of pile section 500. The function of protrusions 502 are similar to the function of textured pattern 402 in the embodiment of FIG. 3. In alternative embodiments of the present disclosure, protrusions 502 may be non-circular but may for example be any other regular shape, such as an oval, or square.

FIG. 5 shows a side view of a pair of pile sections 600 a, 600 b according to an embodiment of the present disclosure. Each pile section 600 a, 600 b comprises a castellations at an axial end. The castellations of first pile section 600 a are sized and shaped to interlock with the castellations of second pile section 600 b. This is achieved by the provision of female alignment portion 602 a, and the provision of male alignment portion 602 b. When first pile section 600 a is brought together with second pile section 600 b, the respective alignment portions fit within one another and prevents pile sections 600 a, 600 b from experiencing any radial or circumferential displacement. Advantageously, in embodiments in which pile sections 600 a, 600 b comprise channels (such as those of FIG. 2), the castellations enable a more straightforward alignment of the vertical channels of adjoining pile sections.

FIG. 6 shows a plan view of pile section 700 according to an embodiment of the present disclosure. Pile section 700 is composed of three equally sized pre-cast concrete section components 702, 704, 706. When the section components 702, 704, 706 are assembled together, they form a concrete cylinder that is pile section 700. To facilitate alignment, each section component comprises protrusion 702 b and recess 702 a at each end. Protrusion 702 b interlocks with recess 704 b of adjacent pile section 704. Likewise, recess 702 a interlocks with protrusion 704 a of the same adjacent pile section 704. The protrusions and recesses ensure that once the pile sections are in position, the pile sections are only free to move in an axial direction, and are fully restricted in the radial and circumferential directions. Assembling the pile section from a plurality of section components allows the pile sections to be readily transported (as section components, that can typically be stacked or otherwise efficiently stored).

FIG. 7 shows a plan view of pile section 800 according to an embodiment of the present disclosure. Pile section 800 is composed of five equally sized pre-cast concrete section components 802, 804, 806, 808, and 810. When the section components 802, 804, 806, 808, and 810 are assembled together, they form a hollow concrete pentagon that is pile section 800.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, the pile sections need not necessarily be circular cylindrical. The pile sections may be other shapes such as polygonal. It may be that the section components of the pile sections are configured such that they can form different shaped/sized polygonal sections by altering the angle of the join between adjacent section components and/or by choosing differently sized section components.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments. 

What is claimed is:
 1. A method of forming a pile within a bore, the method comprising: stacking a plurality of hollow pile sections end-to-end within the bore to form a column, there being a gap between at least a part of an outside surface of the column and the surface of the bore; filling the gap with a curable liquid material; and curing the liquid material.
 2. The method of claim 1, wherein the pile sections are tubular pile sections, preferably having the same inner diameter.
 3. The method of claim 1, further include the preceding step of joining together a plurality of section components to form each pile section.
 4. The method of claim 1 wherein the curable liquid material is grout.
 5. The method of claim 1 including the step of pouring the curable liquid material directly into the gap.
 6. The method of claim 1, the method including the step of directing the curable liquid material into the gap through channels in the pile sections.
 7. (canceled)
 8. A pile within a bore, comprising: a column comprising a stack of a plurality of hollow pile sections arranged end-to-end within the bore, and a cured material between at least a part of an outside surface of the column and the surface of the bore.
 9. The pile within a bore of claim 8, wherein the column tapers in width.
 10. The pile within a bore of claim 8, wherein the pile sections comprise elements at each of their axial ends, the axial end elements being sized and shaped to interlock with the corresponding axial end elements of another of the pile sections.
 11. The pile within a bore of claim 8, wherein the pile sections include channels configured to allow the transport of a curable liquid material along the length of the column.
 12. The pile within a bore of claim 8, wherein the pile sections are pre-fabricated concrete.
 13. (canceled)
 14. The pile within a bore of claim 8, wherein the pile is load-bearing within a building.
 15. A kit of parts for forming a pile within a bore, the kit comprising: a plurality of pile sections, wherein the plurality of hollow pile sections are configured to be stacked end-to-end to form a column, the number of pile sections corresponds to a length of the column, said length being equal to at least half of the depth of the bore; and a curable liquid material.
 16. The method of claim 2, further including the preceding step of joining together a plurality of section components to form each pile section.
 17. The method of claim 3, wherein the curable liquid material is grout.
 18. The method of claim 4, including the step of pouring the curable liquid material directly into the gap.
 19. The method of claim 5, the method including the step of directing the curable liquid material into the gap through channels in the pile sections.
 20. The pile within a bore of claim 9, wherein the pile sections comprise elements at each of their axial ends, the axial end elements being sized and shaped to interlock with the corresponding axial end elements of another of the pile sections.
 21. The pile within a bore of claim 10, wherein the pile sections include channels configured to allow the transport of a curable liquid material along the length of the column.
 22. The pile within a bore of claim 11, wherein the pile sections are pre-fabricated concrete. 